The present invention relates, in a first aspect, to a method for finding a thread end with a cop preparation station as well as a cop preparation station .
Cop preparation stations in accordance with the first aspect are located between a rewinding machine and a spinning machine and are, as a rule, integrated into the rewinding machine. The spinning machine delivers thread packages with a relatively small diameter which are wound on sleeves and which are called cops. The thread end of a cop which arises is released from the surface of the thread package by a thread finding means, which can consist of a suction nozzle and of a brush, in order to enable a subsequent automatic thread connection in the rewinding machine. The thread end position, i.e. the location at the surface of the thread package where the thread end is normally located can be different and depends on the execution of the spinning machine. Most ring spinning machines have for example no integral doffer and deliver cops with an underwinding although ring spinning machines with integral doffers, which are increasingly being used, deliver the cops with a reserve winding or jacket winding.
Occasionally cops are also encountered with a top winding. In order to operate with compatible machines the manufacture of the rewinding machine includes a thread finding means in the thread preparation station which is matched to the nature of the thread end position. For reasons of economy only about 15 seconds is available for the detection and search process of the thread finding means. When the thread end cannot be found in this time interval the relevant cop is ejected and is automatically returned to the cop preparation station where an operator periodically passes by in order to inspect the faulty cops, to release the thread end by hand and to bring it into the correct thread end position. With an increased occurrence of cripple cops, the use of an operator is no longer sufficient. As referenced herein, "cripple" cops are cops which do not conform to an ideal shape due, for example, to improper formation. These cops thus constitute irregularly shaped cops. It can then transpire that such cripple cops are repeatedly ejected onto the return loop during each search process which can lead to cop queues due to an assembly of cops improperly retained at the spinning machine and to non-utilised winding stations at the rewinding machine. For example, a case of this kind can occur when with a thread break the operator at the spinning machine applies or winds onto the cop an auxiliary thread, without connection, instead of connecting the thread end on the cop located in the spinning location with an auxiliary thread. The upper end of the auxiliary thread is set in both cases in the region of the outlet rolls of the drafting mechanism. Thus cop thread packages arise with several part lengths of fibers, the thread ends of which are initially detected to a large degree in the cop preparation station whereafter the cops enter into the rewinding machine. Here these cops are unwound up to the end of a part length of thread and are then separated out, whereupon the cripple cops which arise in this way reach the return guidance loop again. In the cop preparation station the cripple cops are again subjected to the contact of the brushes whereby the quality of the thread suffers and, since the thread end has still not been found are separated out again. It is to be assumed that this is the reason why the piecing process of the service robot by means of an auxiliary thread--without connection--was therefore not able to establish itself in practice.
It is the object of the invention, in its first aspect, to increase the economy and the degree of efficiency of a cop preparation station and thus of the entire rewinding machine, even in the presence of cops having thread lengths in several parts and cripple cops of all kinds, using the simplest means, and simultaneously to reduce the number of service personnel. The thread should also be more carefully treated.
At this point DE-OS 37 42 348 should be mentioned, which has only been recently published, the object of which is to make it possible "to successfully find a thread end for almost all spools". In order to achieve this object, an airflow control plate is provided close to the outer periphery of the thread package of the cop and an air nozzle is provided in the gap which is formed in this way and blows upwardly parallel to the longitudinal axis of the cop with the object of bringing a thread end which hangs downwardly not in the predetermined position into the region of a thread detection means. In the event that the thread end is located on the upper slope of the thread package of the cop it will be evident, in particular after studying the subsequent description, that the thread end cannot be released by upward blowing.
Furthermore, reference is made to the cop preparation station described in DE-OS 36 32 459 which effects an appropriate adaptation of the thread search operation in order to distinguish between cops with S and Z turns. This adaptation lies in the fact that the direction of cop rotation during the searching process is selected in accordance with this turn.